1. Field of the Invention
The present invention relates to a heat-developable photosensitive material, which may be referred to as a “photosensitive material” hereinafter, used suitably for medical diagnosis, industrial photography, printing and COM; and a method of producing the same.
2. Description of the Related Art
In recent years, it has been intensely demanded to reduce processing liquid waste from the viewpoint of environmental preservation and saving space in the fields of films for medical diagnosis and films for photographic plate-making. Thus, technique on heat-developable photosensitive materials is necessary as films for medical diagnosis and films for photoengraving which make it possible to form distinct black images having high resolution and sharpness. According to these heat-developable photosensitive materials, it is possible to supply to customers a simpler heat-developable processing system which does not require any processing chemical agent which is a solution or damage environment.
Similar matters are also demanded in the fields of ordinary image forming materials. Particularly in the field of films for medical diagnosis, a high image-quality, which is superior in sharpness and graininess, is necessary since delicate depiction is required. Moreover, diagnosis is required to be easily attained. From these viewpoints, an image having a cool tone is preferred. At present, various hard copy systems using pigment or dye, such as an inkjet printer and electrophotography, are in circulation as ordinary image forming systems. However, no hard copy system is satisfactory as an output system for medical images. Thermal image forming systems using an organic silver salt are described in, for example, U.S. Pat. Nos. 3,152,904 and 3,457,075, and “Thermally Processed Silver Systems” (Imaging Processes and Materials, Neblette 8th version, written by D. Klosterboer and edited by J. Sturge, V. Walworth, and A. Shepp, Chap. 9, p. 279, 1989). In particular a heat-developable photosensitive material in general has a photosensitive layer wherein a catalyst-activating amount of a photocatalyst (for example, silver halide), a reducing agent, a reducible silver salt (for example, an organic silver salt), and optionally, a color adjusting agent for controlling a color tone of silver are dispersed in a matrix of a binder. The heat-developable photosensitive material is imagewise exposed to light, heated to a high temperature (for example, 80° C.) to cause redox reaction between the reducible silver salt (functioning as an oxidizer) and the reducing agent, thereby forming a black silver image. The redox reaction is promoted by catalytic action of a latent image of the silver halide generated by the exposure. Therefore, the black silver image is formed in the exposed area. Fuji Medical Dry Imager FM-DP L, which is disclosed in a great number of documents, examples of which include U.S. Pat. No. 2,910,377 and Japanese Patent Application Publication No. 43-4924, has been sold as a system for forming medical images.
In the production process of the heat-developable photosensitive material, a photosensitive layer is formed on a substrate. An undercoat layer is usually deposited on the substrate in order to raise the adhesion between the substrate and the photosensitive layer. Moreover, in the production process, foreign matters such as dust, dirt and fragments of the coating-film are easily generated. These result in various problems. One of them is a problem that if foreign matters such as dust, dirt and fragments of the coating-film are present on the substrate at the time of forming the undercoat layer, troubles such as a repellence defect and a streaking defect, resulting from these foreign matters, happen in the undercoat layer and thus a bad effect is also produced in the photosensitive layer formed thereon, so that a defect is generated in the heat-developable photosensitive material itself. Similarly, if the undercoat layer is formed and subsequently a foreign matter is present on the layer, the following problem arises: a bad effect is also produced in the photosensitive layer, so that a defect is generated in the heat-developable photosensitive material itself.
Particularly in the case in which the photosensitive layer contains silver behenate, the photosensitive layer is brittle and is affected by the state of the undercoat layer. Therefore, there is a problem that the above-mentioned defects are markedly generated. For photosensitive materials required to have a high image quality, for example, photosensitive materials for medical diagnosis, this problem is serious. Thus, it is intensely demanded to solve this problem.